Tweet
Hi everyone. I'm new to this forum but have read countless posts by others trying to diagnose and resolve my overheating issue. There appears to be a wealth of knowledge here and I'm hoping that knowledge can help me out of this situation and back on the water.
I recently bought a pre-owned, 2001 Caribe (14' RIB) which has been repowered with a 2015 Yamaha T50 LB. When I tested it before purchasing it ran on the hose flawlessly for quite some time. My first time taking it out (and every time thereafter) I have faced overheating and low oil pressure alarms. I believe the low oil pressure is the result of the oil getting too hot, but wanted to share this detail in the event is alters someone's approach when thinking about potential causes for this issue. What's strange is that the motor performs well at cruising speeds but when I throttle down for a No Wake zone or to put it back on the trailer, the alarm horn IMMEDIATELY sounds and the high temp or low oil pressure lights illuminate on the tach (old analog tach).
In the interest of responsible boat maintenance and to resolve what I'd think would be 95% or more of the issues, I replaced the engine oil (Yamalube 10W-30) and filter, lower unit oil, spark plugs, water pump (impeller, cup, gaskets, woodruff key, O-ring, but not the housing), and for good measure the thermostat. The problem persisted. From reading other posts here, i thought there might be a blockage in the cooling lines, water jacket or exhaust cover. I was really hoping that it was the pencil anode breaking and blocking flow, as tony_dix experienced, but the anode was intact. With the exhaust, cover removed i took the opportunity to blow compressed air and jets of water through the cooling pathways to try to free any blockages caused by corrosion or foreign object. The water jet seemed to work, especially when I covered some of the other outlets leading to the cylinders to focus flow to the others. I'll note that through the use of an IR thermometer I've identified the source of the hot spot as Cylinder #1, so that cooling channel was my primary focus. I also identified a blockage in one of the water passages for the fuel cooler and was able to clear it.
I've tried to isolate and troubleshoot every aspect of the cooling system I can think of, but haven't been able to resolve the overheating issue. My best guess is that at low RPM insufficient water is being circulated to adequately cool the motor. I've also been running it with the thermostat removed. This provides marginal improvement but hasn't resolved the issue. I also thought that Cylinder #1's injector could be partially blocked causing it to run lean (and hot), and the hot spot couldn't be cooled with low-RPM water flow rates. I swapped two of the injectors but the problem persists.
I've found only one thing that keeps it from overheating, but it's not a viable solution for operation on the water... When I operate the motor on the hose (ear muffs) with the thermostat removed (haven't tried this with it installed) AND have a second hose attached to the factory flush device the motor doesn't overheat. As a data point, when operating with ear muffs only, very little cooling water exits the exhaust via the prop, but substantial volumes are discharged here with both hoses attached.
Lastly, I discovered that the tell-tale was robbing what little water pressure I have at idle. When I covered the tell-tale with my finger the motor cooled itself more efficiently. This may be an unpopular practice but I removed the tell-tale from the cooling loop and it has helped, but I realize this is a band-aid on stab wound and not a perfect solution.
I've attempted to list and describe everything I've tried, but I'm sure there's more I've tried and don't readily recall. I've been working on this with every free moment I have for the past month or so. Any help that someone more experienced than I can offer would be greatly appreciated.
Garrett
I recently bought a pre-owned, 2001 Caribe (14' RIB) which has been repowered with a 2015 Yamaha T50 LB. When I tested it before purchasing it ran on the hose flawlessly for quite some time. My first time taking it out (and every time thereafter) I have faced overheating and low oil pressure alarms. I believe the low oil pressure is the result of the oil getting too hot, but wanted to share this detail in the event is alters someone's approach when thinking about potential causes for this issue. What's strange is that the motor performs well at cruising speeds but when I throttle down for a No Wake zone or to put it back on the trailer, the alarm horn IMMEDIATELY sounds and the high temp or low oil pressure lights illuminate on the tach (old analog tach).
In the interest of responsible boat maintenance and to resolve what I'd think would be 95% or more of the issues, I replaced the engine oil (Yamalube 10W-30) and filter, lower unit oil, spark plugs, water pump (impeller, cup, gaskets, woodruff key, O-ring, but not the housing), and for good measure the thermostat. The problem persisted. From reading other posts here, i thought there might be a blockage in the cooling lines, water jacket or exhaust cover. I was really hoping that it was the pencil anode breaking and blocking flow, as tony_dix experienced, but the anode was intact. With the exhaust, cover removed i took the opportunity to blow compressed air and jets of water through the cooling pathways to try to free any blockages caused by corrosion or foreign object. The water jet seemed to work, especially when I covered some of the other outlets leading to the cylinders to focus flow to the others. I'll note that through the use of an IR thermometer I've identified the source of the hot spot as Cylinder #1, so that cooling channel was my primary focus. I also identified a blockage in one of the water passages for the fuel cooler and was able to clear it.
I've tried to isolate and troubleshoot every aspect of the cooling system I can think of, but haven't been able to resolve the overheating issue. My best guess is that at low RPM insufficient water is being circulated to adequately cool the motor. I've also been running it with the thermostat removed. This provides marginal improvement but hasn't resolved the issue. I also thought that Cylinder #1's injector could be partially blocked causing it to run lean (and hot), and the hot spot couldn't be cooled with low-RPM water flow rates. I swapped two of the injectors but the problem persists.
I've found only one thing that keeps it from overheating, but it's not a viable solution for operation on the water... When I operate the motor on the hose (ear muffs) with the thermostat removed (haven't tried this with it installed) AND have a second hose attached to the factory flush device the motor doesn't overheat. As a data point, when operating with ear muffs only, very little cooling water exits the exhaust via the prop, but substantial volumes are discharged here with both hoses attached.
Lastly, I discovered that the tell-tale was robbing what little water pressure I have at idle. When I covered the tell-tale with my finger the motor cooled itself more efficiently. This may be an unpopular practice but I removed the tell-tale from the cooling loop and it has helped, but I realize this is a band-aid on stab wound and not a perfect solution.
I've attempted to list and describe everything I've tried, but I'm sure there's more I've tried and don't readily recall. I've been working on this with every free moment I have for the past month or so. Any help that someone more experienced than I can offer would be greatly appreciated.
Garrett
Comment